As communications technologies advance, the number of communications protocols and applications are increasing. There is growing demand for multi-purpose devices that can support multiple protocols or applications. Such devices typically include separate circuitries for different purposes, resulting in increased complexity and cost.
For example, multi-band Orthogonal Frequency Division Multiplexing (OFDM) devices typically employ Inverse Fast Fourier Transform (IFFT) circuitry for frequency to time domain conversion in transmitters and Fast Fourier Transform (FFT) circuitry for time to frequency domain conversion in receivers. The current proposal for ultra wideband (UWB) according to Multi-band OFDM Alliance (MBOA) 802.15.3a standard suggests a 128-point IFFT/FFT implementation that includes 128 inputs and 128 outputs. It may be useful for compatibility reasons to make the transmitters and receivers configurable so that other implementations (such as a 64-point IFFT/FFT implementation that includes 64 inputs and 64 outputs) are also supported. A typical approach for implementing a configurable 64-point and 128-point IFFT/IFFT involves using two independent IFFT/FFT circuitries and switching between them. The 64-point IFFT/FFT circuitry can be implemented using either a radix-4 core or a radix-2 core. The 128-point IFFT/FFT circuitry can also be implemented using a radix-4 or a radix-2 core. A radix-4 core is typically more complex computationally and consumes more power than a radix-2 core. It would be desirable if multi-purpose devices such as dual mode 802.11 a/g and UWB transceivers could be implemented without requiring multiple independent circuitries, so that lower device size and cost could be achieved. It would also be useful if such devices could operate more efficiently, and could easily switch between different modes.